Lighting assembly with high irradiance

ABSTRACT

A lighting module and a lighting assembly provide high irradiance at long working distances. The lighting module includes at least two rows of multiple LEDs separated from each other by an intermediate area between the rows and one integral optical element on top of the at least two rows of multiple LEDs. The one integral optical element includes one collimator lens portion per row of LEDs extending along the row of LEDs. The collimator lens portions of different rows are merged together above the intermediate area. The collimator lens portions, seen in a direction perpendicular to the at least two rows, provide an off-axis focus for the one collimator lens portion, and focus light emitted from the at least two rows of multiple LEDs in a focus line extending parallel to the rows of LEDs at a focus distance above the optical element.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/614,681, filed on Nov. 18, 2019, which is a § 371 application ofInternational Application No. PCT/EP2018/061807, filed on May 8, 2018,which claims the benefit of EP Patent Application No. 17171721.8, filedon May 18, 2017, which are incorporated by reference as if fully setforth.

FIELD OF INVENTION

The invention relates to a lighting module providing a high irradianceat a long working distance, a lighting assembly comprising multiplelighting modules, methods to manufacture the lighting module as well asthe lighting assembly and use of the lighting modules or lightingassemblies.

BACKGROUND

UV curing technology is utilized for curing inks, coatings, adhesivesand other commercially useful UV sensitive materials throughpolymerization. While traditional mercury vapor lamps can be replaced incertain low UV intensity applications with LED based UV curing systems,it is more difficult to use LEDs as a replacement for high intensityapplications. LED sources and LED systems have a relatively low outputpower compared to mercury-arc lamps. LED arrays are used at very closerange to the material which poses the risks of the curing system cominginto contact with the substrate that is being cured.

Consequently, there is a need for high irradiance LED UV systems with along working distance.

SUMMARY

It is an object of the present invention to provide a high irradianceLED system with a long working distance.

The invention is defined by the independent claims. The dependent claimsdefine advantageous embodiments.

According to a first aspect a lighting module is provided. The lightingmodule comprises at least two rows of multiple LEDs separated from eachother by an intermediate area between the rows, where the rows arearranged on a front side of a printed circuit board, and one integraloptical element on top of the multiple LEDs in order to shape lightemitted from each of the multiple LEDs, where the optical elementcomprises one collimator lens portion per row of LEDs extending alongthe row of LEDs, where the collimator lens portions of different rowsare merged together above the intermediate area in order to form the onesingle optical element, where the collimator lens portions seen in adirection perpendicular to the row of LEDs are shaped in order toprovide an off-axis focus for each of the collimator lens portions,where the shapes are adapted to each other in order to focus the lightemitted from the rows of LEDs in a focus line extending parallel to therows of LEDs at a focus distance above the optical element. Theindividual collimator lens portions seen in a direction perpendicular tothe row of LEDs are each shaped asymmetrically with respect to a firstreference plane comprising the optical axis of the respective row ofLEDs, wherein the first reference plane is parallel to the rows of LEDs.The individual collimator lens portions may be arranged symmetrically orasymmetrically to each other with respect to a second reference planewhich is perpendicular to a plane comprising the rows of LEDs and whichcomprises the focus line. The asymmetric arrangement with respect to thesecond reference plane may be used to adapt the position of the focusline parallel to the plane comprising the rows.

The term “LED” denotes any solid state lighting light source. LEDs aretypically small (less than 4 mm.sup.2) and available e.g. ranging fromvisible and ultraviolet wavelengths with very high brightness. LEDs havemany advantages over incandescent light sources including lower energyconsumption, longer lifetime, improved physical robustness, smallersize, and faster switching.

A row of multiple LEDs denote a linear arrangement of multiple LEDsadjacent to each other forming a line of LEDs, especially a straightline of LEDs. A printed circuit board (PCB) denotes the mechanicalsupport, which electrically connects the components arranged on theprinted circuit board (here the LEDs) using conductive tracks, pads andother features prepared onto a non-conductive substrate. Componentsmight be soldered or adhesively bonded on the PCB. Advanced PCBs maycontain components embedded in the substrate. For high-density LEDarrays it is crucial to have effective heat transfer from the LED arrayto the heat sink (typically copper). For this, typically,copper-substrate PCBs or ceramic PCB are commonly used because of thehigh thermal conductivity.

The term “optical element” denotes any element acting upon light passingthrough said element. The optical element is an at least partiallytransparent body suitably shaped to act upon the light in the desiredway causing refraction, diffraction, reflection or blocking parts of thelight beam passing the optical element. A collimator as an opticalelement narrows the light beam in a specific direction, e.g. focusingthe light beam on a focus point having a focus distance to thecollimator or optical element comprising the collimator. The term“collimator lens portion” denotes an optical element comprising acollimator lens as a part (portion) of the optical element. The term“off-axis focus” denotes a focus point deviating from the optical axisof the element providing the focused beam, here the collimator lensportions.

This invention improves the peak irradiance by using the specified opticon a LED array. The lighting module according to the present inventionprovides a high irradiance LED system with a long working distanceenabling, e.g. for curing purposes or other high power LED applications.In case of using the lighting module for curing purposes, e.g. as alight source within a curing apparatus, the LEDs can be arranged at asecure distance to the to-be-cured material avoiding the risk of thecuring apparatus, especially the light source of the curing apparatus,coming into contact with the material that is being cured. Curing mightbe applied to organic materials, e.g. where monomers are converted intopolymers in order to harden the material. This is especiallyadvantageous in case of curing materials which passes the light sourcewith high velocities, e.g. in continuous curing processes for flatsheets of material.

The lighting module may be arranged in such a way that the rows of LEDsare arranged parallel to each other. A parallel arrangement enables toachieve a closer packaging of the multiple LEDs and provides a definedfocus at some height above the optic in the direction along the rows ofLEDs.

The lighting module may be arranged in such a way that the LEDs arelight emitters with a peak wavelength of less than 460 nm, preferablythe LEDs are UV-light emitting LEDs. Curing is a process during whichultraviolet light and visible light is used to initiate a photochemicalreaction that generates a crosslinked network of polymers. Somecomposite resins might be cured at peak wavelengths of 360 nm or 388 nm.UV Curing is adaptable to printing, coating, decorating, stereographyand assembling of a variety of products and materials. This is madepossible by some of its key attributes, it is: a low temperatureprocess, a high speed process, and a solventless process since curing isby polymerization rather than by evaporation.

The lighting module may be arranged in such a way that the LEDs in eachrow of the LEDs are closely packed to each other. The gap between twoadjacent LEDs can be less than half of the adjacent LED center-to-centerdistance in this case.

There are two important factors that determine the curing quality: totaldose and peak irradiance. In order to achieve both increased dose andpeak irradiance, LEDs must be closely packed together. Packaging thatallows greater number of LEDs to be more densely fit into a defined areahave an advantage over less dense solutions.

High-power LEDs can be separated in two categories: chip-scale packagesand conventional domed packages. The former has a total outer dimensionclose to the internal emitting area of the LED. Such LEDs offer a veryhigh packing density and therefor a high flux density while theindividual LED efficiency is typically somewhat lower than theconventional domed packages. The dome of conventional domed packages,typically a silicone or glass, improves the extraction efficiency oflight out of the LED, but is also forces the outer package dimensions tobe significantly larger than the internal LED emitting area. Forcollimating purposes, an array of chip-scale packages is advantageous asthough an optic, the higher flux density allows higher irradiance atsome distance above the optic.

The lighting module may be arranged in such a way that the collimatorlens portions are so-called total internal reflectance (TIR) collimatorportions. These make use of total internal reflection (TIR) to directlight towards a light emitting surface. An optical element is denoted asa TIR element when collimating the light rays from the light emitter,both by reflecting them and by refracting them. Theoretically, all ofthe light produced by the emitter is gathered by the TIR element, herethe TIR collimator portions. A TIR element takes advantage of “totalinternal reflection” where light that strikes a surface at a shallowangle will bounce off the surface and continue through the materialinstead of refracting. The TIR collimator portion collimates the lightand sends a concentrated beam of light out in the same direction, givinga tight hotspot with greater throw. A typical TIR element looks like acone with a hole where the point should be extending about halfwaythrough the lens. This hole fits over the LED and any rays that strikethe flat bottom (bottom is curved to focus the light instead of lettingit pass straight through) of the hole will go straight out the front,giving a small hotspot.

The lighting module may be arranged in such a way that each of the TIRcollimator portions comprise an inner refractive surface building arecess to enclose the row of LEDs on its light emitting side, an outerreflective surface facing away from the LEDs and a light emittingsurface, wherein the inner refractive surface has a first and a secondentrance surface to direct entering light emitted from the row of LEDstowards the light emitting surface of the TIR collimator portion, wherethe first entrance surface is suitably shaped to collimate the enteringlight directly towards the light emitting surface, whereby the secondentrance surface is suitably shaped to direct the entering light towardsthe outer reflective surface, and where the outer reflective surface issuitably shaped to collimate the portion of the light entered into theTIR collimator portion via the second entrance surface towards the lightemitting surface. This collimator shape provides a focused light beamwith improved brightness. The lighting module may be arranged in such away that the light emitting surfaces of each of the merged TIRcollimator portions establish a single light emitting surface of theoptical element.

The lighting module may be arranged in such a way that a cooling elementis attached to the printed circuit board on a backside of the printedcircuit board. Close packing of high power LEDs leads to thermalcrowding which lowers the efficiency. With the cooling element theefficiency is increased.

According to a second aspect a lighting assembly comprising multiplelighting modules according to the present invention is provided, wherethe lighting modules are arranged next to each other in order to alignthe rows of LEDs of each lighting module to the rows of the neighboredlighting modules to establish continued rows of LEDS across the multiplelighting modules. The modular concept of the lighting assembly enablesthe adaption to the length of the lighting assembly to the demandedlength for the particular application of the lighting assembly as alight source. Also the lighting assembly provides a high irradiance LEDsystem with a long working distance with adaptable length of the focusline along the rows of LEDs at the focus distance.

The lighting assembly may be arranged in such a way that the opticalelements of each lighting module are established by one optical assemblyelement extending along the continued rows of LEDs across the multiplelighting modules. On one hand the optical assembly element across alllighting modules provides an improved mechanical stability of thelightings assembly and on the other hand ensures the same focusproperties for all LEDs arranged in the rows across the multiplelighting modules.

The lighting assembly may be arranged in such a way that an assemblycooling element is arranged on a backside of the lighting assemblyestablished by all backsides of the lighting modules. Close (dense)packing of high power LEDs leads to thermal crowding which lowers theefficiency. With the assembly cooling element the efficiency isincreased for all LEDs of all lighting modules ensuring the LEDs workingwith essentially the same efficiency along the row of LEDs.

According to a third aspect a method to manufacture a lighting moduleaccording to the present invention is provided. The method comprises thesteps of

Arranging multiple LEDs in at least two rows of LEDs separated from eachother by an intermediate area between the rows on a front side of aprinted circuit board, preferably the rows of LEDs are arranged parallelto each other; and

Arranging one integral optical element on top of the multiple LEDs inorder to shape light emitted from each of the multiple LEDs, where theoptical element comprises one collimator lens portion per row of LEDsextending along the row of LEDs, where the collimator lens portions ofdifferent rows are merged together above the intermediate area in orderto form the one single optical element, where the collimator lensportions seen in direction perpendicular to the row of LEDs are shapedin order to provide an off-axis focus for each of the collimator lensportions, where the shapes are adapted to each other in order to focusthe light emitted from the rows of LEDs in a focus line extendingparallel to the rows of LEDs at a focus distance above the opticalelement,

Preferably further comprising the step of attaching a cooling element tothe printed circuit board on a backside of the printed circuit board.

The method according to the present invention enables manufacturing of alighting module providing a high irradiance LED system with a longworking distance enabling.

According to a fourth aspect a method to manufacture a lighting assemblyaccording to the present invention is provided. The method comprises thesteps of

arranging multiple lighting modules according to the present inventionnext to each other, and

aligning the rows of LEDs of each lighting module to establish continuedrows of LEDs across the multiple lighting modules,

preferably further comprising the step of arranging an assembly coolingelement on a backside of the lighting assembly established by allbacksides of the lighting modules.

The method may be arranged in such a way that it further comprises thestep of establishing the optical elements of each lighting module by oneoptical assembly element extending along the continued rows of LEDsacross the multiple lighting modules.

According to a fifth aspect a use of a lighting module or a lightingassembly both according to the present invention as a light source formaterial curing purposes is provided. The established light source of acuring apparatus can be arranged at a secure distance to the to-be-curedmaterial avoiding the risk of the curing apparatus, especially the lightsource of the curing apparatus, coming into contact with the materialthat is being cured.

It shall be understood that a preferred embodiment of the invention canalso be any combination of the dependent claims with the respectiveindependent claim.

Further advantageous embodiments are defined below.

BRIEF DESCRIPTION OF THE DRAWING(S)

These and other aspects of the invention will be apparent from andelucidated with reference to the embodiments described hereinafter.

The invention will now be described, by way of example, based onembodiments with reference to the accompanying drawings.

In the drawings:

FIG. 1 shows a principle sketch of the lighting module according to thepresent invention (a) in a top view onto the front side, (b) in a topview onto the backside, and (c) in a side view.

FIG. 2 shows a principle sketch of the lighting assembly according tothe present invention (a) in a top view onto the front side, (b) in atop view onto the backside, and (c) in a perspective view.

FIG. 3 shows a principle sketch of the optical element focusing thelight emitted from the rows of LEDs of a lighting module or lightingassembly according to the present invention.

FIG. 4 shows the peak irradiance as a function of the distance from theoptical element of lighting modules with and without an optical elementas shown in FIG. 1-3.

FIG. 5 shows a principle sketch of the method to manufacture thelighting module according to the present invention.

FIG. 6 shows a principle sketch of the method to manufacture thelighting assembly according to the present invention.

FIG. 7 shows a principle sketch of the use of the lighting module or thelighting assembly for curing purposes.

In the Figures, like numbers refer to like objects throughout. Objectsin the Figs. are not necessarily drawn to scale.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Various embodiments of the invention will now be described by means ofthe Figures.

FIG. 1 shows a principle sketch of the lighting module according to thepresent invention (a) in a top view onto the front side, (b) in a topview onto the backside, and (c) in a side view. The lighting module 1comprises two rows 21, 22 of eleven LEDs 2 each which are closelypacked. The rows are separated from each other by an intermediate area23 between the rows 21, 22. The rows 21, 22 are arranged parallel toeach other on a front side 31 of a printed circuit board 3 furthercomprising electrical contacts 33 to operate the rows of LEDs. Theprinted circuit board 3 might be fixed to another substrate, holder orhousing (not shown here) by screws 9 or other fixing means. The lightingmodule 1 further comprises one integral optical element 4 on top of theLEDs 2 in order to shape light 5 emitted from each of the multiple LEDs2, where the optical element 4 comprises one collimator lens portion 41,42 per row 21, 22 of LEDs extending along the row 21, 22 of LEDs. Thecollimator lens portions 41, 42 of different rows 21, 22 are mergedtogether above the intermediate area 23 in order to form the one singleoptical element 4, where the collimator lens portions 41, 42 seen in adirection perpendicular to the row 21, 22 of LEDs are shaped in order toprovide an off-axis focus F (see FIG. 3) for each of the collimator lensportions 41, 42. The shapes are adapted to each other in order to focusthe light 5 emitted from the rows 21, 22 of LEDs in a focus line FL (seeFIG. 3) extending parallel to the rows 21, 22 of LEDs at a focusdistance FD (see FIG. 3) above the optical element 4. The collimatorlens portions 41, 42 are in this embodiment each shaped asymmetricallywith respect to a first reference plane comprising the optical axis OA(see FIG. 3) of the respective individual collimator lens portion or row21, 22 of LEDs, wherein the first reference plane is parallel to therows 21, 22 of LEDs. The collimator lens portions 41, 42 are in thisembodiment shaped mirror symmetric to each other with respect to asecond reference plane which is perpendicular to a plane comprising therows 21, 22 of LEDs and which comprises the focus line FL. The opticalelement 4 might be made of glass or transparent plastic material. TheLEDs 2 might be light emitters with a peak wavelength of less than 460nm. In an embodiment the LEDs 2 are UV-light emitting LEDs.

FIG. 1b shows the lighting module 1 from its backside, where a coolingelement 6 is attached to the printed circuit board 3 on a backside 32 ofthe printed circuit board 3.

FIG. 1c shows the optical element 4 in more details in a side view,where the collimator lens portions 41, 42 of the optical element 4 areso-called TIR collimator portions, where each of the TIR collimatorportions 41, 42 comprise an inner refractive surface 4 i building arecess 24 to enclose the row 21, 22 of LEDs on its light emitting side 2a, an outer reflective surface 4 o facing away from the LEDs 2 and alight emitting surface 4 e, wherein the inner refractive surface 4 i hasa first and a second entrance surface 4 i 1, 4 i 2 to direct enteringlight 5 emitted from the row 21, 22 of LEDs towards the light emittingsurface 4 e of the TIR collimator portion 41, 42, where the firstentrance surface 4 i 1 is shaped as a asymmetric lens to collimate theentering light 5 directly towards the light emitting surface 4 e, wherethe second entrance surface 4 i 2 is shaped as a circular wall aroundthe LEDs 2 to direct the entering light 5 towards the outer reflectivesurface 4 o, and where the outer reflective surface 4 o has a tulip-likeshape to collimate the portion of the light 5 entered into the TIRcollimator portion 41, 42 via the second entrance surface 4 i 2 towardsthe light emitting surface 4 e. The reflection at reflective outersurface 40 is in this embodiment due to TIR. The reflective outersurface may alternatively have a metal coating in order to supportreflection of the light 5 towards the light emitting surface 4 e, wherethe thickness of the metal coating is adapted to be reflect all lighttowards the emitting surface 4 e. Here the light emitting surfaces 4 eof each of the merged TIR collimator portions 41, 42 establish a singleflat light emitting surface 4 e of the optical element 4. The opticalelement 4 is fixed in a holder 34 attached to the printed circuit boardor being part of the printed circuit board, e.g. by clamping. The holder34 is arranged outside the emitting surfaces 2 a of the LEDs and thedesigned light path for the optical element 4 and the application of thelighting module 1.

FIG. 2 shows a principle sketch of the lighting assembly 10 according tothe present invention (a) in a top view onto the front side, (b) in atop view onto the backside, and (c) in a perspective view. The lightingassembly 10 in this embodiment comprises three lighting modules 1according to FIG. 1 where the lighting modules 1 are arranged next to(beside of) each other in order to align the rows 21, 22 of LEDs 2 ofeach lighting module 1 to the rows 21, 22 of the neighbored lightingmodules 1 to establish continued rows 21, 22 of LEDs 2 across themultiple lighting modules 1. Compared to the single lighting module 1 ofFIG. 1 the focus line is three times longer enabling the processing oflarger material samples. FIG. 2b shows the backside 10 b of the lightingassembly 10, where an assembly cooling element 8 is arranged on thebackside 10 b established by all backsides 32 of the lighting modules 1of the lighting assembly 10. FIG. 2c shows the lighting assembly 10 in aperspective view where the optical elements 4 of each lighting module 1are established by one single optical assembly element 7 extending alongthe continued rows 21, 22 of LEDs 2 across the multiple lighting modules1, which is fix to the holders 34 of each lighting module 1, e.g. viaclamping. The optical assembly element might be made of the samematerials as the optical elements of each lighting module 1.

FIG. 3 shows a principle sketch of the optical element 4 focusing thelight 5 emitted from the rows 21, 22 of LEDs 2 of a lighting module 1 orlighting assembly 10 according to the present invention. The collimatorlens portions 41, 42 are each shaped asymmetrically in order to providean off-axis focus F for each of the collimator lens portions 41, 42,where the asymmetrical shapes are adapted to each other in order tofocus the light 5 emitted from the rows 21, 22 of LEDs in a focus lineFL extending parallel to the rows 21, 22 of LEDs at a focus distance FDabove the optical element 4. The optical axes OA of each row of LEDs incase of no present optical element are indicated as dashed lines. Theoptical element 4 shown here has a length parallel to the rows 21, 22 ofLEDs of 50 mm, a width perpendicular to the rows 21, 22 of LEDs of 30 mmand a height above the printed circuit board 3 of 10 mm. At a distanceof 50 mm above the emitting surface 4 e of the optical element 4 thebeam of light 5 has a full width at half of the maximum intensity of 22mm. For purpose of optical analysis, the lengths of the rows are assumedto be infinitely long. The individual collimator lens portions 41, 42are in this embodiment only slightly asymmetrically to each other withrespect to a second reference plane (not shown) which is perpendicularto the plane comprising the rows 21, 22 of LEDs and which comprises thefocus line FL. The asymmetry of the individual collimator lens portions41, 42 to each other may be used to shift the focus line FL (which is inthis embodiment perpendicular to the plane of FIG. 3) parallel to theplane comprising the rows 21, 22 of LEDs which may be represented by thesurface of the printed surface board 3 to which the LEDs are attachedto.

FIG. 4 shows the peak irradiance PI as a function of the distance D fromthe optical elements 4 of lighting modules 1 with and without opticalelements 4 as shown in FIG. 1-3. The peak irradiance was obtained from arow of neighboring lighting modules operated of 176 W optical outputpower each and comprising two rows 21, 22 of LEDs being closed packedwith 22 LEDs per row of 4 mm.sup.2 FlipChip UV-LEDs offering highirradiance. The curve C2 was obtained from these lighting modules 1without optical elements 4 arranged above the rows 21, 22 of LEDs. C2shows relatively high peak irradiances larger than 8 W/cm.sup.2 at smalldistances below 20 mm steeply decreasing below 2 W/cm.sup.2 fordistances above 70 mm. The curve C1 relates to a row of neighboringlighting modules 1 according to the present invention with opticalelements 4. Here the peak irradiance PI is above 10 W/cm.sup.2 up to adistance D of 50 mm and is above 8 W/cm.sup.2 up to a distance of 65 mm.At a distance D of 100 mm the peak irradiance PI for lighting modules 1with optical elements 4 is more than a factor two higher the peakirradiance for lighting modules without an optical element. This showsthat the lighting modules according to the present invention is able toprovide a high irradiance LED system with a long working distance of 10W/cm.sup.2 at a distance of 50 mm, which is a practical distance forusing the lighting module for curing purposes avoiding the risk of thelighting module 1 coming into contact with the to-be-cured material.

FIG. 5 shows a principle sketch of the method 100 to manufacture thelighting module 1 according to the present invention. The method 100comprises the steps of arranging 110 multiple LEDs in at least two rows21, 22 of LEDs separated from each other by an intermediate area 23between the rows 21, 22 on a front side 31 of a printed circuit board 3,where the rows 21, 22 of LEDs are preferably arranged parallel to eachother; and arranging 120 one integral optical element 4 on top of themultiple LEDs 2 in order to shape light 5 emitted from each of themultiple LEDs 2, where the optical element 4 comprises one collimatorlens portion 41, 42 per row 21, 22 of LEDs extending along the row 21,22 of LEDs, where the collimator lens portions 41, 42 of different rows21, 22 are merged together above the intermediate area 23 in order toform the one single optical element 4, where the collimator lensportions 41, 42 seen in direction perpendicular to the row 21, 22 ofLEDs are each shaped asymmetrically in order to provide an off-axisfocus F for each of the collimator lens portions 41, 42, where theasymmetrical shapes are adapted to each other in order to focus thelight 5 emitted from the rows 21, 22 of LEDs in a focus line FLextending parallel to the rows 21, 22 of LEDs at a focus distance FDabove the optical element 4. In an embodiment the method 100 furthercomprises the step of attaching 130 a cooling element 6 to the printedcircuit board 3 on a backside 32 of the printed circuit board 3.

FIG. 6 shows a principle sketch of the method 200 to manufacture thelighting assembly 10 according to the present invention. The method 200comprises the steps of arranging 210 multiple lighting modules 1 next toeach other and aligning 220 the rows 21, 22 of LEDs of each lightingmodule 1 to establish continued rows 21, 22 of LEDs across the multiplelighting modules 1. In an embodiment the method 200 further comprisesthe step of arranging 230 an assembly cooling element 8 on a backside 10b of the lighting assembly 10 established by all backsides 32 of thelighting modules 1. In an alternative embodiment, where the lightingmodules 1 being arranged next to each other and the rows of LEDs arealigned and the lighting modules do not comprise optical elements themethod 200 may comprise the step of establishing 240 the opticalelements 4 for each lighting module 1 by placing one single opticalassembly element 7 extending along the continued rows 21, 22 of LEDs 2into the holder 34 of the multiple lighting modules 1.

FIG. 7 shows a principle sketch of the use 300 of the lighting module 1or the lighting assembly 8 as a light source 20 for material curingpurposes in a curing apparatus, where the LEDs 2 can be arranged at asecure distance to the to-be-cured material avoiding the risk of thecuring apparatus, especially the light source 20 of the curingapparatus, coming into contact with the material that is being cured.Curing might be applied to organic materials, e.g. where monomers areconverted into polymers in order to harden the material. This isespecially advantageous in case of curing material which passes thelight source with high velocities, e.g. in a continuous curing processesfor flat sheets of material.

While the invention has been illustrated and described in detail in thedrawings and the foregoing description, such illustration anddescription are to be considered illustrative or exemplary and notrestrictive.

From reading the present disclosure, other modifications will beapparent to persons skilled in the art. Such modifications may involveother features which are already known in the art and which may be usedinstead of or in addition to features already described herein.

Variations to the disclosed embodiments can be understood and effectedby those skilled in the art, from a study of the drawings, thedisclosure and the appended claims. In the claims, the word “comprising”does not exclude other elements or steps, and the indefinite article “a”or “an” does not exclude a plurality of elements or steps. The mere factthat certain measures are recited in mutually different dependent claimsdoes not indicate that a combination of these measures cannot be used toadvantage.

Any reference signs in the claims should not be construed as limitingthe scope thereof.

LIST OF REFERENCE NUMERALS

-   1 lighting module according to the present invention-   2 LED(s)-   2 a light emitting surface of the LED(s)-   21 a (first) row of LEDs-   22 a (second) row of LEDs-   23 intermediate area between the rows of LEDs-   24 recess above the LEDs established by the collimator lens portions-   3 printed circuit board (PCB)-   31 frontside of the PCB-   32 backside of the PCB-   33 electrical contacts of the PCB-   34 holder to fix the optical element to the PCB-   4 optical element-   4 i inner refractive surface of the collimator lens portions-   4 i 1 first entrance surface of the inner refractive surface-   4 i 2 second entrance surface of the inner refractive surface-   4 o outer reflective surface of the collimator lens portions/optical    element-   4 e light emitting surface of the collimator lens portions-   41 collimator lens portion assigned to one row of LEDs-   42 collimator lens portion assigned to another row of LEDs-   5 light emitted from the LED(s)-   6 cooling element-   7 optical assembly element-   8 assembly cooling element-   9 fixing means (e.g. a screw)-   10 lighting assembly according to the present invention-   10 b backside of the lighting assembly-   20 light source for a material curing process-   100 method to manufacture the lighting module according to the    present invention-   110 Arranging multiple LEDs in at least two separate rows of LEDs-   120 Arranging one integral optical element on top of the multiple    LEDs-   130 attaching a cooling element to the printed circuit board-   200 method to manufacture the lighting assembly according to the    present invention-   210 arranging multiple lighting modules next to each other-   220 aligning the rows of LEDs of each lighting module to establish    continued rows of LEDs across the multiple lighting modules-   230 arranging an assembly cooling element on a backside of the    lighting assembly-   240 establishing the optical elements of each lighting module by one    optical assembly element-   300 Use of a lighting module/assembly as a light source for material    curing-   C1 peak irradiance as a function of D for a lighting module with    optical element-   C2 peak irradiance as a function of D for a lighting module without    optical element-   D distance from optical element-   F off-axis focus of the collimator lens portions of the rows of LEDs-   FD focus distance between optical element of of-axis focuses-   FL focus line provided by the optical element-   OA optical axis-   PI Peak irradiance of the light emitted from the LEDs

What is claimed is:
 1. A lighting system comprising: a printed circuitboard; a first row of ultra-violet (UV) light-emitting diodes (LEDs) ona surface of the printed circuit board; a second row of UV LEDs on thesurface of the printed circuit board and spaced apart from the first rowof UV LEDs; and an optical element comprising at least a firstcollimator lens portion, a second collimator lens portion, and a thirdportion above both the first and second collimator lens portions, theoptical element disposed over the printed circuit board with the firstcollimator lens portion over the first row of UV LEDs and the secondcollimator lens portion over the second row of UV LEDs, each of thefirst and second collimator lens portions comprising: a recess in theoptical element that encloses the first or second row of UV LEDs, therecess forming an inner refractive surface that comprises a firstentrance surface configured to direct light from the first or second rowof UV LEDs toward the third portion and a second entrance surfaceconfigured to direct light from the first or second row of UV LEDs in alateral direction within the optical element, and an outer reflectivesurface facing away from the UV LEDs configured to collimate the lightthat enters the integral optical element via the second entrance surfacein the lateral direction toward the third portion.
 2. The lightingsystem of claim 1, wherein the first row of UV LEDs is parallel to thesecond row of UV LEDs.
 3. The lighting system of claim 1, wherein the UVLEDs have peak wavelengths of less than 460 nm.
 4. The lighting systemof claim 1, wherein the UV LEDs are spaced apart within each of thefirst and second rows with adjacent UV LEDs having a gap between themhaving a distance less than half of a center-to-center distance betweenthe adjacent UV LEDs.
 5. The lighting system of claim 1, furthercomprising a cooling element thermally coupled to a surface of theprinted circuit board opposite the surface on which the LEDs aredisposed.
 6. The lighting system of claim 1, wherein the first entrancesurface is asymmetric with respect to an optical axis of the respectivefirst or second collimator lens portion.
 7. The lighting system of claim1, wherein the outer reflective surface surrounds the respective recessin the optical element.
 8. The lighting system of claim 1, wherein theoptical element is an integral optical element and the third portionconnects the first and second collimator lens portions.
 9. The lightingsystem of claim 1, wherein the lighting system has a peak irradiance(PI) above 10 W/cm² up to a distance of 50 mm.
 10. A lighting systemcomprising: a plurality of lighting modules, each of the plurality oflighting modules comprising: a first row of ultra-violet (UV)light-emitting diodes (LEDs) on a surface of the printed circuit board,a second row of UV LEDs on the surface of the printed circuit board andspaced apart from the first row of UV LEDs, and an optical elementcomprising at least a first collimator lens portion, a second collimatorlens portion, and a third portion above both the first and secondcollimator lens portions, the optical element disposed over the printedcircuit board with the first collimator lens portion over the first rowof UV LEDs and the second collimator lens portion over the second row ofUV LEDs, each of the first and second collimator lens portionscomprising: a recess in the optical element that encloses the first orsecond row of UV LEDs, the recess forming an inner refractive surfacethat comprises a first entrance surface configured to direct light fromthe first or second row or UV LEDs toward the third portion and a secondentrance surface configured to direct light from the first or second rowof UV LEDs in a lateral direction within the optical element, and anouter reflective surface facing away from the UV LEDs configured tocollimate the light that enters the integral optical element via thesecond entrance surface in the lateral direction toward the thirdportion, each of the plurality of lighting modules arranged next to eachother with the first row of UV LEDs aligned for each of the plurality ofmodules and the second row of UV LEDs aligned for each of the pluralityof modules to form a continuous first row of UV LEDs and a continuoussecond rows of UV LEDs across each of the plurality of lighting modules.11. The system of claim 10, wherein the optical element comprises asingle integral optical element over all of the plurality of lightingmodules.
 12. The system of claim 10, further comprising a single coolingelement thermally coupled to all of the plurality of lighting modules atsurfaces of the printed circuit board opposite the surface on which theUV LEDs are disposed.
 13. The system of claim 10, wherein the contiguousfirst row of UV LEDs is parallel to the contiguous second row of UVLEDs.
 14. The system of claim 10, wherein the UV LEDs have peakwavelengths of less than 460 nm.
 15. A method of manufacturing alighting system, the method comprising: arranging a plurality ofultra-violet (UV) LEDs in one of a first row or a second row on asurface of at least one printed circuit board to form at least onelighting module; and obtaining an optical element comprising at least afirst collimator lens portion, a second collimator lens portion, and athird portion above both the first and second collimator lens portions,each of the first and second collimator lens portions comprising: arecess in the optical element that encloses the first or second row ofUV LEDs, the recess forming an inner refractive surface that comprises afirst entrance surface configured to direct light from the first orsecond row or UV LEDs toward the third portion and a second entrancesurface configured to direct light from the first or second row of UVLEDs in a lateral direction within the optical element, and an outerreflective surface facing away from the UV LEDs configured to collimatethe light that enters the integral optical element via the secondentrance surface in the lateral direction toward the third portion; andarranging the optical element over the UV LEDs with the first collimatorlens portion over the first row of UV LEDs and the second collimatorlens portion over the second row of UV LEDs.
 16. The method of claim 15,wherein the at least one lighting module comprises a plurality oflighting modules, and the method further comprises: arranging theplurality of light modules next to each other; and aligning the firstrow of UV LEDs in each module and aligning the second row of UV LEDs ineach module to form a continuous first row of UV LEDs and a continuoussecond rows of UV LEDs across each of the plurality of lighting modules.17. The method of claim 16, wherein the arranging the optical elementover the UV LEDs comprises arranging one optical element over all of theplurality of lighting modules.
 18. The method of claim 16, furthercomprising attaching a single cooling element to surfaces of the printedcircuit board of each of the plurality of modules opposite the surfaceon which the UV LEDs are disposed.
 19. The method of claim 15, furthercomprising attaching a cooling element to a surface of the circuit boardopposite the surface on which the UV LEDs are disposed.